NASA’s Curiosity rover on Mars captured on February 2, 2023 how rays of sunlight illuminated a cloud bank as the ‘king star’ set over the horizon.
These ‘sunrays’ are also known as crepuscular rays. It was the first time that the sun’s rays were seen so clearly on Mars.
Curiosity captured the scene during the rover’s latest twilight cloud survey, which builds on its 2021 observations of noctilucent, or night-glow, clouds. While most Martian clouds are no more than 60 kilometers above the ground and are made up of water ice, the clouds in the latest images appear to be at higher altitudes, where it is especially cold. That suggests these clouds are made of carbon dioxide ice, or dry ice.
Just like on Earth, clouds provide scientists with complex but crucial information for understanding climate. By observing when and where clouds form, scientists can learn more about the composition and temperatures of the Martian atmosphere, as well as the winds that blow within it.
The 2021 cloud survey included more images taken by Curiosity’s black-and-white navigation cameras, which provided a detailed view of a cloud’s structure as it moved. But the recent study, which began in January and will end in mid-March, relies more on the rover’s Mastcam color camera, which helps scientists see how cloud particles grow over time.
In addition to the image of the sun’s rays, Curiosity captured a set of colored feather-shaped clouds on January 27. When illuminated by sunlight, certain types of clouds can create a rainbow-like spectacle called iridescence.
“cloudwe see iridescence, it means that the size of the particles in a cloud is identical to that of its neighbors in every part of the cloud”, explains in a statement Mark Lemmon, an atmospheric scientist at the Boulder Institute of Space Sciences, in Colorado. “By looking at the color transitions, we see that the size of the particles changes throughout the cloud. That tells us about the way the cloud is evolving and how its particles are changing size over time.”
Curiosity captured both the sun’s rays and iridescent clouds as panoramas, each of which was composited from 28 images sent back to Earth. The images have been processed to bring out the highlights.
NASA discovers that Venus could become a new home for the inhabitants of planet Earth
Archival NASA data supports that Venus may be losing heat from geological activity in regions called coronas, possibly as early tectonic activity on Earth.
Earth and Venus are rocky planets with a similar size and chemical composition., so they should lose their internal heat to space at about the same rate. How Earth loses heat is well known, but the mechanism of heat flow from Venus has long been a mystery.
A study using data from three decades ago from NASA’s Magellan mission has taken a new look at how Venus cools and found that thin regions of the planet’s upper layer may provide an answer.
Our planet has a hot core that heats the surrounding mantle. which transports that heat to the rigid outer rocky layer of the Earth, or lithosphere. The heat is then lost to space, cooling the upper region of the mantle. This mantle convection drives tectonic processes at the surface, keeping a mosaic of moving plates in motion. Venus lacks plate tectonics, so planetary science has long wondered how it loses heat and what processes shape its surface.
The study addresses this mystery by drawing on observations by the Magellan spacecraft in the early 1990s of nearly circular geologic features on Venus called coronae. Running new measurements of the coronas visible in the Magellan images, the researchers concluded that coronae tend to be situated where the planet’s lithosphere is thinnest and most active.
“For a long time we have clung to the idea that the Venusian lithosphere is stagnant and thick, but our view is evolving,” said Suzanne Smrekar, a research scientist at NASA’s Jet Propulsion Laboratory, who led the study published in Nature Geoscience.
Just as a thin sheet releases more body heat than a thick duvet, a thin lithosphere allows more heat to escape from the planet’s interior. through floating plumes of molten rock that ascend to the outer layer. Normally, when heat flux increases, subsurface volcanic activity increases. Thus, the coronae probably reveal places where active geology is shaping the surface of Venus today.
The researchers focused on 65 previously unstudied coronas, up to a few hundred kilometers in diameter. To calculate the thickness of the surrounding lithosphere, they measured the depth of the trenches and ridges surrounding each crown.
They found that the ridges are closer together in areas where the lithosphere is more flexible or elastic. Using a computer model of how an elastic lithosphere bends, they determined that, on average, the lithosphere around each coronal is about 11 kilometers thick, much less than previous studies suggest. These regions have an estimated heat flux higher than the Earth average, suggesting that the coronas are geologically active.
“Although Venus does not have similar tectonics to Earth, these regions of thin lithosphere appear to be leaking significant amounts of heat.similar to areas where new tectonic plates are forming on the Earth’s seafloor,” says Smrekar.
*With information from Europa Press